Computerized Tomography has grown in sophistication along with the computers or central processing units (CPU's) that made such tomography possible. In MRI systems, even today's sophisticated CPU's are taxed into operating at the limits of their capacity. The control commands are often changed during the test (scans for the imaging of a patient) in addition to being changed prior to individual scans. Also, there are many more variables in MRI systems than in prior modalities. For example, among the factors varied from test to test and during a test are: the various gradients, the Rf signal amplitude, timing duration, frequency and shape. The control signals and patterns thus have to command analog and/or on-off type operators as well as meticulously shape wave forms for the Rf signal.
The MRI system tests acquire data giving information on T1, T2 and T*2 in addition to acquiring the actual FID signals. The computers are used to control the acquisition of the data and to process the acquired data to form the images. The variations in the control commands for the processing and the acquisition of data in the past have generally been under the direct control of the CPU. The many operations which must be performed by CPU's in MRI systems require expensive large computers or combinations of computers to accomplish the operations in a time efficient manner. Hence those skilled in the art have for many years been seeking ways and means to more effectively control MRI systems from a cost, time and versatility stand point.
It should be understood that while the pattern generators and controllers described herein are described with reference to MRI systems, the invention is broad enough to cover pattern generators and controllers in general. A pattern as used herein means a train of data.
Accordingly and object of the present invention is to provide new and improved controllers including pattern generators that are extremely fast and versatile without requiring large computers or combinations of computers.
Yet, another object of the invention is to provide controllers that operate as computers without arithmetic logic units.
According to the present invention pattern generator and controller arrangements are provided for controlling components of an MRI system, said pattern generator and controller arrangements comprising:
a plurality of channels, PA1 said plurality of channels including a main channel and output channels PA1 said main channel comprising means for controlling the operation of at least some of said output channels responsive to instructions received from a CPU prior to the commencement of a cycle, and PA1 each of said at least some of said output channels including means for supplying outputs for individualized control of the MRI system components.
A related feature of the invention is that the CPU is not burdened by the necessity of directly controlling the patterns sent to the various components of the MRI system. For example, the gradient signals including the encoding gradients, the timing of the gradient pulses, and the Rf pulses including the timing, duration, frequency, shape, and amplitudes of such pulses are controlled by the channels based on data placed in the channels prior to the scan cycles with the CPU released during the scan cycles.
The output channels include memory means. The output patterns are inputted to the particular output channel that provide the desired output patterns to the system components. The patterns are transmitted from the memory means of the output channels under the control of the main channel.
The above named and other objects and features of the present invention will be better understood when considered in the light of the following description taken in conjunction with the accompanying drawings; wherein: